An antiplatelet drug (antiaggregant), also known as a platelet agglutination inhibitor or platelet aggregation inhibitor, is a member of a class of pharmaceuticals that decrease platelet aggregation and inhibit thrombus formation. They are effective in the arterial circulation where classical Vitamin K antagonist anticoagulants have minimal effect.
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets (thrombocytes) and fibrin to form a blood clot to prevent blood loss. Even when a blood vessel is not injured, blood clots may form in the body under certain conditions. A clot, or a piece of the clot, that breaks free and begins to travel around the body is known as an embolus.
A thrombus, colloquially called a blood clot, is the final product of the blood coagulation step in hemostasis. There are two components to a thrombus: aggregated platelets and red blood cells that form a plug, and a mesh of cross-linked fibrin protein. The substance making up a thrombus is sometimes called cruor. A thrombus is a healthy response to injury intended to stop and prevent further bleeding, but can be harmful in thrombosis, when a clot obstructs blood flow through healthy blood vessels in the circulatory system.
Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism of coagulation involves activation, adhesion and aggregation of platelets, as well as deposition and maturation of fibrin.
Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems moving parts of the body. As clotting factors and platelets are used up, bleeding may occur. This may include blood in the urine, blood in the stool, or bleeding into the skin. Complications may include organ failure.
Fibrinogen is a glycoprotein complex, produced in the liver, that circulates in the blood of all vertebrates. During tissue and vascular injury, it is converted enzymatically by thrombin to fibrin and then to a fibrin-based blood clot. Fibrin clots function primarily to occlude blood vessels to stop bleeding. Fibrin also binds and reduces the activity of thrombin. This activity, sometimes referred to as antithrombin I, limits clotting. Fibrin also mediates blood platelet and endothelial cell spreading, tissue fibroblast proliferation, capillary tube formation, and angiogenesis and thereby promotes revascularization and wound healing.
Thrombolysis, also called fibrinolytic therapy, is the breakdown (lysis) of blood clots formed in blood vessels, using medication. It is used in ST elevation myocardial infarction, stroke, and in cases of severe venous thromboembolism.
Low-molecular-weight heparin (LMWH) is a class of anticoagulant medications. They are used in the prevention of blood clots and treatment of venous thromboembolism and in the treatment of myocardial infarction.
Thrombophilia is an abnormality of blood coagulation that increases the risk of thrombosis. Such abnormalities can be identified in 50% of people who have an episode of thrombosis that was not provoked by other causes. A significant proportion of the population has a detectable thrombophilic abnormality, but most of these develop thrombosis only in the presence of an additional risk factor.
Tirofiban, sold under the brand name Aggrastat, is an antiplatelet medication. It belongs to a class of antiplatelets named glycoprotein IIb/IIIa inhibitors. Tirofiban is a small molecule inhibitor of the protein-protein interaction between fibrinogen and the platelet integrin receptor GP IIb/IIIa and is the first drug candidate whose origins can be traced to a pharmacophore-based virtual screening lead.
Bivalirudin (Bivalitroban), sold under the brand names Angiomax and Angiox and manufactured by The Medicines Company, is a specific and reversible direct thrombin inhibitor (DTI).
Direct thrombin inhibitors (DTIs) are a class of medication that act as anticoagulants by directly inhibiting the enzyme thrombin. Some are in clinical use, while others are undergoing clinical development. Several members of the class are expected to replace heparin and warfarin in various clinical scenarios.
Vorapaxar is a thrombin receptor antagonist based on the natural product himbacine, discovered by Schering-Plough and developed by Merck & Co.
The fibrinolysis system is responsible for removing blood clots. Hyperfibrinolysis describes a situation with markedly enhanced fibrinolytic activity, resulting in increased, sometimes catastrophic bleeding. Hyperfibrinolysis can be caused by acquired or congenital reasons. Among the congenital conditions for hyperfibrinolysis, deficiency of alpha-2-antiplasmin or plasminogen activator inhibitor type 1 (PAI-1) are very rare. The affected individuals show a hemophilia-like bleeding phenotype. Acquired hyperfibrinolysis is found in liver disease, in patients with severe trauma, during major surgical procedures, and other conditions. A special situation with temporarily enhanced fibrinolysis is thrombolytic therapy with drugs which activate plasminogen, e.g. for use in acute ischemic events or in patients with stroke. In patients with severe trauma, hyperfibrinolysis is associated with poor outcome. Moreover, hyperfibrinolysis may be associated with blood brain barrier impairment, a plasmin-dependent effect due to an increased generation of bradykinin.
Knoll Pharmaceuticals was a drug development company founded by Albert Knoll and Hans Knoll in Germany in 1886. The company was taken over by German BASF in 1975, which sold it to Abbott Laboratories on 30 June 2002 for $6.9 billion.
Darexaban (YM150) is a direct inhibitor of factor Xa created by Astellas Pharma. It is an experimental drug that acts as an anticoagulant and antithrombotic to prevent venous thromboembolism after a major orthopaedic surgery, stroke in patients with atrial fibrillation and possibly ischemic events in acute coronary syndrome. It is used in form of the maleate. The development of darexaban was discontinued in September 2011.
Direct thrombin inhibitors (DTIs) are a class of anticoagulant drugs that can be used to prevent and treat embolisms and blood clots caused by various diseases. They inhibit thrombin, a serine protease which affects the coagulation cascade in many ways. DTIs have undergone rapid development since the 90's. With technological advances in genetic engineering the production of recombinant hirudin was made possible which opened the door to this new group of drugs. Before the use of DTIs the therapy and prophylaxis for anticoagulation had stayed the same for over 50 years with the use of heparin derivatives and warfarin which have some well known disadvantages. DTIs are still under development, but the research focus has shifted towards factor Xa inhibitors, or even dual thrombin and fXa inhibitors that have a broader mechanism of action by both inhibiting factor IIa (thrombin) and Xa. A recent review of patents and literature on thrombin inhibitors has demonstrated that the development of allosteric and multi-mechanism inhibitors might lead the way to a safer anticoagulant.
Venombin A is an enzyme. This enzyme catalyses the following chemical reaction
The haemostatic system involves the interaction of proteins in the blood, the blood vessel wall and the flow of blood to control bleeding and blood clotting. Developmental Haemostasis is a term that represents the maturation of the haemostatic system from birth to adulthood. There are differences in the concentration, structure and activity of many proteins involved in blood clotting. These changes play an important role in physiological development and are important in providing appropriate diagnosis and treatment of bleeding and clotting disorders. The age-specific differences in the blood clotting system may contribute to the fact that children are less prone to developing thrombosis compared to adults.
Neurobiological Technologies, Inc. ("NTI") was a biotechnology company that was founded in 1987 by Enoch Callaway and John B. Stuppin to in-license and develop drugs primarily to treat neurological conditions; the company was dissolved in 2009 after the failure of its drug candidate ancrod in a Phase III trial for ischemic stroke.
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